I'd like to add a thought that has been bothering me since Dave first called me to discuss the results he had gotten back.
It wouldn't be necessarily correct to make the assumption, based upon the chemistry alone, that the lower grade barrel steels were essentially the same, or fell within the same specification.
Part of the process in making steel is achieving the chemical analysis of the melt, while still in the furnace, so that it meets that portion of a specification. Another equally important portion of the manufacturers ability to meet a specification is to also heat treat the material so that it meets the physical requirements. These requirements, at a minimum, include Yield Strength, UTS (Ultimate Tensile Strength) Elongation, and Reduction of Area. These requirements are determined by heat treating with the product, a test bar from the same melt, then machining the test bar to the requirements of one of the several profiles used in Tensile Testing Machines. Varying the temperatures of heat treatment, and the method of cooling from those temps, can make one material, whose chemistry meets a plain scoop of vanilla, to a butterscotch sundae, with whipped cream, nuts and a cherry.
Our larger melt furnaces had capacities of 40,000 lbs. When the furnaces were tapped, into a ladle (hung from a 50 ton overhead crane) garden variety castings were regularly poured from the same heat as propulsion turbine cases for GE Steam Turbine. one casting may have a selling price of $2.50/lb, and another, $10, or more. There is a lot that goes into the processing of steel beyond simply meeting a chemical analysis.
Its unfortunate Dave didn't have samples of a sufficient size to also do physical testing.
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06-18-2014, 08:03 PM
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